This invention relates to a syringe device and more particularly to a nonreusable syringe having an automatically retracting hypodermic needle to prevent reuse of the syringe.
Many communicable diseases are commonly spread by contacting bodily fluids of an infected person. Reuse of hypodermic syringes is one of the most common ways for such contact, particularly among drug users. Various mechanisms are provided in medical facilities for the disposal or destruction of syringes and hypodermic needles after usage. However, it is not uncommon for a medical worker to be scratched or punctured by a needle after usage and before disposal, resulting in injury and exposure to disease.
Various syringes have been devised for retracting the needle into the syringe or otherwise disarming the syringe after it has been used. U.S. Pat. No. 4,874,382 to Lindemann et al. discloses a safety syringe having a needle which is retracted into a protective sheath inside the syringe. After the needle has been used, it may be withdrawn into the sheath by a coil spring which is actuated by the user depressing a trigger mechanism. However, such a device provides no protection against a user desiring to reuse the syringe who would simply not activate the mechanical trigger.
Another device shown in U.S. Pat. No. 4,838,869 to Allard also provides a protective sheath within the syringe into which the hypodermic needle is withdrawn after usage. In this device, depression of the syringe plunger engages protrusions holding the spring loaded needle so as to release the needle for retraction into the sheath. However, the use of a protective sheath substantially reduces the volume available in the syringe for fluid. Moreover, the strength of the spring is substantially limited by restricting its size to the diameter of the sheath, limiting the effectiveness of overcoming friction of the seal against the needle so as to retract the needle. Furthermore, the use of an inner sheath in a syringe restricts the view of the user in detecting undesirable bubbles in the syringe fluid.